Ground vehicles used in agriculture usually comprise pneumatic tires, which create the interface to the ground. The tires have to support the weight of the vehicle on the one hand while providing the required traction on the other. In very heavy vehicles, for example, in self-propelled harvesters, relatively high surface pressures result below the contact surfaces in spite of very broad tires with six or more individual wheels. These high surface pressures can lead to an impermissibly high soil compaction especially in wet farmlands. Even a reduced internal pressure of tires cannot change much about this problem since in the case of a clearly reduced tire pressure as would be desirable per se for traveling on soft or wet farmlands, the load on the tires is reduced as a result of which the weight of the vehicle can no longer be supported. This relates particularly to vehicles having a greatly fluctuating weight such as e.g. root crop harvesters or the like.
Chain traveling gears or belt-band traveling gears represent a possible alternative for wheeled traveling mechanisms since the effective contact surface can be increased distinctly using a traveling gear of this type, thus enabling an improved transmission of the fraction force on soft and wet farmlands to be realized in most cases. Due to the increasing requirement of protecting the ground and particularly the farmlands used for agriculture from excessively high weight loads resulting from machines and vehicles, those vehicles are being used increasingly which comprise suitable belt-band traveling gears instead of drive wheels and support wheels having pneumatic tires. This is because the former offer a larger contact surface as compared to the tread contacts of rubber wheels and additionally promise an improved traction force on the soft ground. In practice, those traveling gears are used exclusively, in which either all the carrier rollers and deflection rollers are mounted rigidly on a bogie or at most individual small carrier rollers are linked using spring mounting. The reason for this is that the belt-band traveling gears known from prior art require very high pretensioning forces of the belts in order to absorb sufficiently large loads between the carrier rollers. Therefore the hitherto known belt-band traveling gears comprise deflection rollers that are mostly rigidly mounted.
The typical disadvantage of these rigidly mounted deflection rollers is a very limited driving and rolling comfort as compared to a wheeled traveling mechanism, particularly during on-road operation. An additional serious disadvantage of the traveling gears known from prior art is that the resulting contact loads cannot be distributed uniformly on all the carrier and deflection rollers. There exists a uniform load distribution only in the ideal case of absolutely even ground conditions. However, if one carrier roller runs on a bump, the carrier roller is overloaded and the load on the other carrier rollers is relieved resulting in turn in high loads on the grounds.
A traveling mechanism for agricultural machines having resilient belts is known from U.S. Pat. No. 5,409,075 A, in which the track rollers supported on the ground each have a pneumatic suspension system. The pneumatic suspension elements are coupled to one another on the pressure side in order to enable the most uniform possible pressure distribution of the contact surface of the track rollers and the belt in the case of varying ground conditions and ground unevenness.
Another traveling mechanism for agricultural machines having resilient belts is disclosed in DE 196 20 759 A1. The track rollers of the traveling mechanism are each suspended on rocker arms, which are supported against the frame by means of hydraulic control elements. The hydraulic control elements are coupled to one another in an action-oriented manner in order to achieve a spring effect and to be able to ensure constant ground pressures of the track rollers with varying ground factors and ground unevenness.
Finally, DE 601 00 536 T2 describes a belt-band traveling gear for an agricultural tractor, which belt-band traveling gear is supposed to enable an adjustment to varying ground conditions and ground unevenness by means of a spring suspension of the track rollers and the track roller frames. The suspension system comprises several air spring systems by means of which each of the front and rear crawler frames or the individual track rollers are supported.
The known spring systems for belt-band traveling gears or chain traveling gears enable an improved pressure distribution of the effective traveling mechanism contact surfaces between the outer deflection rollers in the case of an uneven ground surface by means of the resiliently suspended track rollers. However, they do not enable any uniform pressure distribution over the entire length of the traveling gear, as a result of which very high pressure peaks are transmitted partially in the farmlands even in the case of traveling mechanisms known from prior art.